I just tried it yesterday for the first time in multiplayer
China has absolutely the most firepower, the GLA or whatever they are called can mostly be called anoying when fighting against them, the usa team is rather medicore though they have some very good units.
One map went like this
We were three against three computer players, but we forgot to pick teams so it ended up being just free for all. I was china and my two friends were gla. One battle me with about 8 of my biggest tangs along with two artilery units went into one of the bases, nuked it first to soften them up a bit and then cleared good part of the base up before leaving because I didnt want to end it so quickly. I just planted all my units in front of both of their bases, a little away though so he could build up again. Then just for fun I started deploying mine fields in my other friends base. When I had about 30 of the biggest units in the area, the guy I attacked first came back with what I thought first was a huge army of tanks and whatnots, I lost two or three tanks in that battle while he lost everything. But meanwhile my other friend the sneaky little bastard managed to get two terrorist inside my base and they blew up nearly all my money making hackers so I had to build them all over again.
Now there was only me, one friend and one of the computer players left, the computer had been been busy fighting one another when all this went on.
In the next big battle my friend finaly found a back way into my base and had a huge army coming for me, so I nuked thew whole army while they were inside my base, a few buildings damaged, lost maybe one, not much. What took me down was that the computer player started to show interested and nuked the base only 5 seconds later!
After this I just stopped playing with them and basicly ran over their bases with ease.
in the end, GLA has NOTHING in the Chinese